Worried

Hello everybody...I have a situation with a girl I really like. But she has a boyfriend who she seems to be lacking interest in based on some things she said to me. This was also confirmed when a friend said that her relationship is not strong. Anyway, I like her and it seems that she has an interest in me based on non-verbal cues from each other. We talked casually and i asked her to go to the gym and she said yes. We didn;t set a day yet howeve because our schedules conflicted. r. I won't have contact with her until Tuesday to set up a day with her. She is with her boyfriend this weekend at a wedding. Im worried that I am going to screw up this whole thing the way I usually do with woman I like. I haven't had an interest in someone like this for a long time because I am finally learning to drop my guard a bit. I am just worried that she is going to back out of going to the gym. This will cause me to feel really bad and I won't get an idea of where she is at with her boyfriend.Typically, I don't interfere with relationships. But this seems different because of the alleged loose ties that she has with him and the non-verbal cues we have been giving each other. I also get worried that someone else will move in on me taking away the opportunity to get to know her. So please any feedback will be helpful. thx